At her birth, Sailor Saturn had lain dormant within her. At the young age of six, she was in an lab accident that took the life of her mother, leaving her badly injured and in a coma. While her father was experimenting on her to save her life, a dark force arrived and made a deal to help him save her. The being provided a Daimon egg, which Dr. Tomoe placed in his daughter, which grew in power within her over the next few years.

Otaku Trivia:

1) Hotaru is the only Sailor Senshi who is reborn after using her powers. The other Senshi stay alive after using their powers apart from Sailor Moon as Princess Serenity.

2) Hotaru is the second youngest Sailor Senshi.

3) Hotaru was the only Sailor Senshi to not receive a name change in the original English dub, but her last name was pronounced differently (pronounced toe-mo instead of toe-mo-eh).